We pick j.root-servers.net, one of the 13 root servers (1), and ask it about inrb.pt and learn that pt is delegated to eight name servers (2), so we ask ns.dns.pt where we learn that inrb.pt is delegated to two name servers, including ns01.fccn.pt (3), so we ask that one and get the following answer:
Inrb.pt is a domain controlled by two domain name servers at fccn.pt having a total of four IP numbers. Some of them are on the same IP network. Incoming mail for inrb.pt is handled by one mail server at inrb.pt themselves.